1. Field of the Invention
The present invention relates to a novel ceric oxide having new and improved morphological properties, and, more especially, a novel ceric oxide having a low content in sulfur. It also relates to the preparation of such novel ceric oxide.
In the description which follows, by the term "specific surface" there is intended the specific B.E.T. surface, determined in accordance with the BRUNAUER-EMMETT-TELLER method described in Journal of the American Chemical Society, 60, 309 (1938).
2. Description of the Prior Art
It is known to this art that ceric oxide, whether alone or in mixture with other metallic oxides, is useful as a catalyst for the synthesis, in particular, of methanol [C. R. Seances, Acad. Sci., Ser. 2, 292 (12), 883-5 (1981)] or in methods for treating residual gases (published Japanese Patent Application No. 76/62,616).
In order to demonstrate good catalytic reactivity, it is desirable to use a ceric oxide which has the greatest possible specific surface.
To date, however, most methods for the preparation of ceric oxide do not enable the attainment of this result.
For example, a method of preparing cerium (IV) oxide by the thermal decomposition of cerium (III) oxalate is known, from the article by S. Horsley, J. M. Towner and M. B. Waldron [Preprints, Symp. Eur. Metall Poudres, 4th, 1, paper 12 (1975)].
The subject treatment, carried out at 450.degree. C., provides a ceric oxide having a specific surface of only 69 m.sup.2 /g.
Compare also R. Sh. Mikhail, R. M. Cagr and R. B. Fahin, J. Appln. Chem., 20, 7, 222-225 (1970) which features the structure of ceric oxide, and reports the characteristics of the ceric oxide prepared by the calcining of ceric hydroxide obtained by treatment of a solution of cerous nitrate with ammonia in the presence of hydrogen peroxide. It is noted, however, that the ceric oxide obtained by calcining at 400.degree. C. has a specific surface of only 80 m.sup.2 /g.